1. Field of the Invention
The present invention relates to a semiconductor laser device that makes it possible to prevent laser bars from thermo-compressively bonding each other without using dummy bars when coating end faces thereof.
2. Background Art
A manufacturing method for semiconductor laser devices includes a process of coating end faces. In the end face coating process, coating films are formed on end faces of semiconductor laser devices to control the reflectance of end faces at a light emitting side and end faces at the opposite side therefrom of semiconductor laser devices. The end face coating process is an important process that significantly influences characteristics, such as threshold values, of semiconductor laser devices.
A conventional manufacturing method for semiconductor laser devices, which includes the end face coating process, will be described. First, a multi-layer structure that permits laser oscillation is formed on a semiconductor substrate. Then, front surface electrodes are formed on the front surface of the semiconductor substrate by Au plating, and rear surface electrodes are formed on the rear surface thereof by Au plating. Next, the semiconductor substrate is cleaved to produce laser bars, each of which having a plurality of semiconductor laser devices with their end faces exposed.
Subsequently, the plurality of laser bars is stacked and clamped by a jig to retain them, and then coating films are formed on the end faces on the light emitting side of the laser bars. In the same manner, coating films are formed on the opposite side faces of the laser bars. After forming the coating films, the laser bars are separated and then, the laser bars are divided into individual semiconductor laser devices. This completes the fabrication of the semiconductor laser devices.
The front surface of the conventional semiconductor laser device obtained as described above is shown in FIG. 7. Referring to FIG. 7, a conventional semiconductor laser device 31 has a front surface electrode 32 formed by Au plating, and also a rear surface electrode (not shown) formed by Au plating.
Coating the end faces with the laser bars in contact with each other, as described above, has been posing the following problem. The heat applied while coating the end faces and the pressure applied to the laser bars when setting them with a jig cause thermo-compressive bonding between the front surface electrodes and the rear surface electrodes, thus preventing the laser bars from being separated after the end face coating. This is because of the mutual thermo-compressive bonding attributable to the fact that the front surface electrodes and the rear surface electrodes of the laser bars are both formed of Au plating.
As a solution to this problem, dummy bars made of Si or the like have been used. More specifically, to coat the end faces, laser bars 33 and dummy bars 34 are alternately disposed and set on a jig 35 so as to prevent the laser bars from directly contacting each other, as shown in FIG. 8 (refer to, for example, Japanese Unexamined Patent Application Publication No. 2000-133871).
The conventional method using such dummy bars, however, has been disadvantageously adding to manufacturing cost and reducing the number of laser bars that can be actually set to a jib.